1. Field of the Invention
The present invention relates to data compression between an encoder and a decoder across a communication channel. More particularly, the present invention relates to toggling between uncompressed data flow and compressed data flow for a communication link whenever the compression ratio is favorable. In addition, this invention relates to negotiating or modifying data compression parameters and achieving algorithm switching for data compression without first interrupting and then restoring the communication link.
2. Description of the Related Art
Existing systems employing data compression (e.g., modem peers on an ITU-T Recommendation V.42 link) can operate in a transparent mode in which characters are transmitted in uncompressed form. The data compression module, (e.g., data compression as described in U.S. Pat. No. 5,955,976 and incorporated by reference herein) is active, but does not influence data transmission.
In existing data compression systems, modification and negotiation of data compression parameters requite that the communication channel is first torn down. In addition, if a switch to a different data compression algorithm is needed, a data communication channel must be torn down and later reestablished in existing communication systems employing V.42 communication links or other similar links.
A need therefore exists for a method and apparatus that allows for modification and negotiation of data compression parameters and for switching to a different data compression algorithm without first tearing down and then reestablishing the communication link. A need also exists for sending uncompressed data across V.42 links or similar links when compression ratios are favorable for such communication.